Field and satellite observations on the seasonal variability of the surface chlorophyll-a in the Bay of La Paz, Gulf of California, Mexico

During 2015–2016, a strong El Nino event, nicknamed the “Godzilla El Nino,” similar to events in 1982–1983 and 1996–1997 occurred in the Pacific Ocean. Based on in situ and satellite observations, this paper aims to assess the water masses and chlorophyll-a surface distribution in the Bay of La Paz, Gulf of California, Mexico, after this event. A conductivity, temperature, and depth (CTD) rosette system equipped with a fluorescence sensor was used to obtain high-resolution measurements and surface water samples for spectrophotometric determinations of chlorophyll-a. Satellite images of sea surface temperature and chlorophyll-a were obtained for the dates when the cruise took place. The results showed the presence of three water masses: Gulf of California Water, Subtropical Subsurface Water, and Pacific Intermediate Water, the last present in Boca Grande. The highest surface chlorophyll-a concentrations observed were 4.51 mg m-3, 4.63 mg m-3, and 1.00 mg m-3 from the fluorescence sensor, spectrophotometric determination, and satellite observations, respectively. The horizontal distribution patterns for the three methods employed matched well. Despite the fact that Godzilla El Nino had several adverse effects in different regions, at the Bay of La Paz, they seem to have had no dramatic effect on the chlorophyll-a at the time of our observations, even though the values observed were higher compared to previous reports. This apparent lack of effect on the surface waters due to this climate disruption could be associated to the seasonal variability of the phytoplankton productivity, which presents a peak during autumn and winter and to the local fertilization mechanisms reported in the study area; however, further observations are required to confirm this.

<i>1940. E. W. Scripps Cruise to the Gulf of California. The Geological Society of America, Memoir 43. Part I. Geology of Islands and Neighboring Land Areas</i>. Charles A. Anderson<i>1940. E. W. Scripps Cruise to the Gulf of California. The Geological Society of America, Memoir 43. Part II. Megascopic Paleontology and Marine Stratigraphy</i>. J. Wyatt Durham<i>1940. E. W. Scripps Cruise to

Long-beaked common dolphins (Delphinus capensis) in the Gulf of California have been exposed to persistent contaminants that originated in large agricultural areas near the coast. Live common dolphins were sampled by remote dart biopsies to determine concentrations of tDDT in blubber. Life stage and initial gender identification was determined by field observations. Gender was confirmed by genetic analysis of the skin. Concentration of tDDT in blubber was analyzed by gas chromatography. The 16 samples collected consisted of: 2 adult males, 6 adult females, and 8 juveniles. 4,4'-DDE was detected in most of the samples with 4,4'-DDD and 4,4'-DDT under detection levels. Concentrations of DDE varied from non-detectable to 87.3 µg/g lipid weight with a median of 16 µg/g lipid weight. The highest concentration was detected in an immature female. No differences were detected between gender or life stage but this could be attributed to small sample size. We recommend continued sampling of D. capensis blubber biopsies from the Gulf of California in order to relate these levels with affected in vitro biomarkers such as mixed function oxidase activity.

Variations of the mitochondrial control region sequence in whale sharks ( Rhincodon typus) from the Gulf of California, Mexico

A number of Satellite Laser Ranging (SLR) sites in the southwest United States and Mexico, in operation for over ten years, have been supporting the global laser network measuring tectonic plate motion and providing information for studies of regional crustal deformation. Observations of the Laser Geodetic Satellite (LAGEOS) collected in 1994 by the transportable satellite laser ranging system, TLRS‐4, at two sites on the Baja peninsula now provide the means to extend the network of fixed stations at Monument Peak and Otay Mountain in southern California and Mazatlan on mainland Mexico. After the third SLR occupation of Ensenada, it's estimated site motion exhibits nearly the full plate rate predicted by the NNR‐NUVEL1A model for a location on the Pacific plate. At the southern tip of the Baja, the motion of Cabo San Lucas has an azimuth that is more westerly than that expected from Pacific modeled motion. This discrepancy in azimuth, in conjunction with the slower SLR recovered velocity for Mazatlan, results in an apparent 6 mm/yr faster spreading rate across the mouth of the Gulf of California than that predicted by the NUVEL‐1A model. The velocities of the Monument Peak and Otay Mountain sites show the expected long‐term difference from Pacific plate motion, due to their proximity to the San Andreas Fault system.

Seasonal and annual variability in particle fluxes in the Gulf of California: A response to climate forcing

The last ten years have shown that Climate Change (CC) is a major global issue to attend to. The integration of its effects into coastal impact assessments and adaptation plans has gained great attention and interest, focused on avoiding or minimizing human lives and asset losses. Future scenarios of mean sea level rises and wave energy increase rates have then been computed, but downscaling still remains necessary to assess the possible local effects in small areas. In this context, the effects of CC on the wave climate in the Gulf of California (GC), Mexico, have received little attention, and no previous studies have tackled the long-term trend of wave climate at a regional scale. In this paper, the long-term trends of the wave height, wave period and wave energy in the GC were thus investigated, using the fifth-generation climate reanalysis dataset (ERA5). The long-term shoreline evolution was also examined from historical Landsat images, so as to identify erosional hotspots where intervention can be prioritized. The results indicate that both the mean and extreme wave regimes in the GC are getting more energetic and that two-thirds of the coast is suffering chronic erosion. A discrepancy between the trends of the wave period and wave height in some regions of the Gulf was also found. Finally, the importance of natural processes, human activity and CC in the shoreline change is highlighted, while addressing the need for future permanent field observations and studies in the GC.

A study is performed on the combination of ground-based and satellite observations for the derivation of cloud properties. Ground-based measurements from a lidar ceilometer and an infrared radiometer were combined with measurements of the NOAA Advanced Very High Resolution Radiometer and Meteosat satellite instruments. Two case studies are presented: a case with streets of fair weather cumuli and a case with a weak cold front involving cumulus, stratus, and cirrus clouds. From the combination of ground-based and satellite observations, a much better description of the cloud field geometry, cloud base, and cloud top can be obtained than with satellite or ground-based observations alone. The combination of satellite retrievals and lidar-ceilometer measurements is promising. This concept is widely applicable because lidar ceilometers are available on airports all over the world and the used infrared sensors are relatively cheap and can easily be installed. This opens the way for a much improved auto...

Based on results from a ROMS numerical model, the dynamics of the Mexican Central Pacific was studied during three years (2003–2005). The model reproduces the mean and seasonal variability of sea surface temperature, as well as mesoscale eddies and meanders from satellite observations. The model adequately represents the main currents in the region: California Current, Mexican Coastal Current, and Gulf of California currents. The Gulf of California currents are linked to the intensificiation of the Mexican Coastal Current and interact in such a way that the lateral shear generates eddies at the entrance to the Gulf of California. The mesoscale eddies were found to have a depth of ~200 m. The eddies generated in the area (internal Rossby radius of deformation, Rd = 40 km) had a diameter L of ~300 km, an orbital speed of 20–30 cm s–1, and a westward translation speed of ~4 cm s–1. Eddies are considered from intermediate to big (L≈ 7.5 Rd, Ro &lt;&lt; 1), show geostrophic dynamics, and present a westward drift due to Coriolis variation with latitude (beta effect). The size of the eddies seems to be related to the weakening of the meridional component of wind stress during the North American monsoon.

The Cerro Prieto geothermal field, considered an active developing rift basin, is located in the southern limits of the Salton Trough tectonic province. The tectonic activity along the Gulf of California–Salton Trough has created spreading centers linked through a set of transform faults. Such faults are characterized by right lateral motion obliquely oriented to the gulf axis, which produces a transtensional stress regime along the Pacific–North American plate boundary. In particular, the Cerro Prieto basin has developed between the major Cerro Prieto and Imperial right-stepping transform faults, which are part of the San Andreas–Gulf of California fault system (figure 1). Both faults are seismically active and have produced several magnitude 7 earthquakes. However, in the past decades only the Imperial fault has produced superficial ground breakage during earthquakes. This is in contrast to earthquake ruptures on the Cerro Prieto fault, which have not extended up to the ground surface, so this fault trace is not yet well-constrained. The epicenter of the 24 May 2006 Mw 5.4 earthquake was located along the northern end of the Cerro Prieto fault. In a field survey performed after the earthquake, superficial fractures were clearly observed at short distances from the epicenter. Based on our field observations, we address the question of whether such fractures are evidence of rupture along the Cerro Prieto fault or are associated with a conjugate fault. ▴ Figure 1. Tectonic map of the Gulf of California region, including the peninsula of Baja California and Sonora, Mexico; California; Arizona; and the main tectonic elements: North American plate, Pacific Plate, East Pacific Rise, Gulf extensional province (GEP), Cerro Prieto fault (CPf), Imperial fault (If), Agua Blanca fault (ABf), Laguna Salada fault (LSf), Elsinore fault (Ef), San Jacinto fault (SJf), San Andreas fault (SAf), and Garlock fault (Gf). On 24 May 2006 at 04:20 (UTC) …

Initiation, evolution and extinction of pull-apart basins: Implications for opening of the Gulf of California

Temporal variability of satellite chlorophyll-a as an ecological resilience indicator in the central region of the Gulf of California

Biology of the subtropical sac-spawning euphausiid Nyctiphanes simplex in the northwestern seas of Mexico: Vertical and horizontal distribution patterns and seasonal variability of brood size

Monthly climatologies are used to estimate the mean seasonal cycle of MODIS-Aqua satellite-derived sea surface temperature (SST), surface chlorophyll (Chl- a ) and their relationship with surface wind stress curl (from the Cross-Calibrate Multi-Platform, CCMP) in the Bay of La Paz located in the southwestern Gulf of California, a region identified as having high biological productivity and significant seasonal variability. Harmonic fit applied to the monthly climatologies of these variables indicate a best fit with annual and semi-annual constituents. The annual amplitude was the dominant signal in both SST and Chl- a , corresponding to the bay-wide seasonal cycle of warming and cooling associated with the influx of upwelled nutrient-rich coastal waters jointly with the water exchange between the bay and the Gulf of California. Empirical orthogonal function (EOF) decomposition yielded the annual and semi-annual patterns of the seasonal cycle that respond to wind forcing. The EOF 1 explained 93% of the SST variance and 48% of the Chl- a variance, showing a homogeneous variability of both variables across the bay and a strong thermal and biological gradient in the vicinity of the Gulf of California with their corresponding amplitude time series representing out-of-phase annual cycles, which corresponded to the regional dynamics of wind forcing pattern. The EOF 2 accounted for 6% of the SST variance and 31% of the Chl- a variance, which reached its peak during winter associated with the high Chl- a anomaly values (>1.5 mg m –3 ) observed along the coast. The intense biological productivity covaried strongly with the wind stress curl annual cycle ( R = 0.5, P < 0.05 ), suggesting that these Chl- a blooms could be associated with coastal currents and upwelling events regulated by the seasonal wind forcing pattern playing an essential role in the modulation of this quasi-permanent biophysical coupling observed in the Bay of La Paz during an annual cycle.

The depth-integrated model (Ψ-Mod) and depth-resolved Kara Sea model (KDRSM) of primary production in the water column were verified using field (2013–2015) and satellite (MODIS-Aqua scanner, 2007, 2011, 2013–2015) observations. The KSDRM and Ψ-Mod over- or underestimate the values of integrated primary production (IPP) in autumn by a factor of 2 and 2.5 with shipboard data as input parameters; the rootmean-square difference (RMSD) was 0.29 and 0.39, respectively. In summer, the efficiency of Ψ-Mod decreased by a factor of 1.5 (RMSD = 0.57), while the predictive capacity of the KSDRM remained the same (RMSD = 0.31). In the Laptev Sea in autumn, the KSDRM performed better than Ψ-Mod (the RMSD was 0.24 and 0.41, respectively). There was no sufficient decrease in the predictive skill of either algorithm when MODIS-Aqua data were used as input parameters. Thus, Ψ-Mod, being a simple and precise algorithm, can be recommended for evaluating the annual IPP in the Kara Sea and for studying its long-term variability using satellite data.